Recently, liquid crystal displays (LCDs) are the most widely used among flat panel displays. Generally, a liquid crystal display has a structure in which a liquid crystal layer is embedded between a thin film transistor (TFT) array substrate and a color filter substrate. When an electric field is applied to electrodes placed on the array substrate and the color filter substrate, an array of liquid crystal molecules of the liquid crystal layer between the above two substrates is changed, whereby an image can be displayed. Polarizing films (polarizing plates) are disposed on outer surfaces of the array substrate and the color filter substrate. The polarizing film can control polarization by allowing selective transmittance of light, which travels in a certain direction among light emitted from a backlight and light passing through a liquid crystal layer. Generally, a polarizing plate includes a polarizer capable of polarizing light in a certain direction, a protective layer, and a compensation film.
Due to the anisotropic refractivity of liquid crystals, a liquid crystal display has fundamental problems relating to viewing angle. Thus, wide viewing angle technologies, such as vertical alignment (VA) modes, horizontal alignment modes (IPS, FFS), and the like, which can improve viewing angle of typical TN (twisted nematic) modes, are widely employed in the art.
Although liquid crystals of the horizontal alignment mode have a disadvantage of slow response time, the horizontal alignment mode has advantages of excellent contrast and excellent viewing angle at tilt angles. On the contrary, although liquid crystals of the vertical alignment mode have advantages of fast response time and excellent contrast when viewed from front, the vertical alignment mode provides unsatisfactory viewing angle due to severe change in polarization state at tilt angles. Therefore, for a liquid crystal display employing liquid crystals in the vertical alignment mode, it is very important to have improved viewing angle, and a compensation film is essential for improved viewing angle.
Although viewing angle-compensation films aligned in a thickness direction have been developed, these films have a structure wherein tilted alignment is formed from a film surface to the interior of the film, thereby causing degradation of contrast ratio (CR).